Thanks for being brave enough to speak up about this and I'm glad to hear that no one was hurt. I know a lot of people like to pretend that mistakes never happen with firearms, but no matter how seriously someone takes safety or how well they are trained, mistakes still happen.
When I was in high school, I lived in a 2 bedroom apartment with my dad. My dad is a Vietnam vet and has always been a very organized and responsible guy (one of the only people I know that starches and irons his jeans regularly). However, one day when I was playing video games in my room with a few friends, I heard a loud pop from the other room. It turned out that my dad was cleaning his gun in his bedroom and missed a bullet in the chamber. We then noticed that the bullet had traveled through the wall into my bedroom, leaving a bullet hole in my closet and then hitting the floor. When we traced the trajectory, we found that it traveled just inches under my friend's ass, under his chair.
So anytime I see someone mock someone else for a firearm accident, I just shake my head. Sure, poor training and awareness will increase the likeliness of accidents, but accidents can still happen to anyone.
It's like that one quote: The difference between a wise man and a fool is that the fool thinks himself to be wise and the wise man knows himself to be a fool.